FERGUSON, Mo. — Federal and state officials unveiled a sweeping response Thursday to clashes between police and protesters over the shooting death of an unarmed black teenager, with Missouri taking over security operations from local police and authorities agreeing to accept Justice Department help in handling protests.

Speaking from Martha’s Vineyard, Mass., President Barack Obama called for national unity after the police shooting Saturday of Michael Brown, 18, in this St. Louis suburb.

“Now is the time for peace and calm on the streets of Ferguson,” Obama said. “Let’s remember that we’re all part of one American family.”

Attorney General Eric Holder Jr. announced a series of steps his department is taking, including a meeting held Thursday with civic leaders to calm tensions and a civil rights probe in which federal investigators have already interviewed witnesses to the shooting.

In unusually blunt remarks, Holder said he was “deeply concerned” about “the deployment of military equipment and vehicles” on Ferguson’s streets. He said that Missouri officials have accepted federal assistance “to conduct crowd control and maintain public safety without relying on unnecessarily extreme displays of force.”

Even as dozens of protesters continued their campaign near the shooting scene for a fifth day Thursday, state officials followed the federal lead.

Missouri Gov. Jay Nixon announced that the Missouri Highway Patrol would take over security operations in Ferguson, led by Capt. Ron Johnson, an African-American who grew up in the area.

“We are going to have a different approach and have the approach that we’re in this together,” Johnson said.

As a result, the heavy riot armor, the SWAT trucks with sniper posts and the gas masks were gone from the streets of Ferguson on Thursday night, and Johnson marched with the crowd, eliciting cheers from the protesters.

Johnson vowed to not blockade the streets, to set up a media staging center, and to ensure that residents’ rights to assemble and protest were not infringed upon.

“I’m not afraid to be in this crowd,” Johnson said to reporters.

Obama’s remarks were the most visible step in a rapid coalescence among political and community leaders to tamp down the violence, as images of riot police, tear gas and government intervention provoked a national debate about race and justice.

In a burst of interest fueled by photos and video of heavily armed police on social media, politicians from both sides of the aisle rushed Thursday — five days after the shooting — to condemn the tactics of the nearly all-white police force in the predominantly black town.

The reactions were remarkably similar across the political spectrum. Sen. Claire McCaskill, D-Mo., called for authorities to “de-militarize this situation,” while Sen. Rand Paul of Kentucky, a likely Republican presidential candidate, condemned “the militarization of our law enforcement” in a Time magazine essay.

Underlying the dispute was the lack of clarity about just what happened Saturday night in Ferguson.

According to a friend who said he witnessed the incident, Brown was walking down a Ferguson street when a police officer in a car ordered him to get on the sidewalk. Brown had his hands in the air to show he was unarmed when the officer shot him multiple times, the friend said.

The police version is that Brown attacked the officer in his car and tried to grab his gun. Ferguson Police Chief Thomas Jackson said during a news conference Wednesday that the officer was struck in the face during the encounter. The side of the officer’s face was “swollen,” Jackson said, and he was treated at an area hospital.

Federal investigators are trying to sort out the conflicting versions of events but are proceeding cautiously and deferring to state investigators for now, a federal law enforcement official said Thursday.

The official, speaking on condition of anonymity to discuss an ongoing investigation, said the investigation is a high priority for the Justice Department and FBI but it is far too early to determine whether charges will be brought.

Holder, who met with Obama on Thursday about the case, said, “Our review will take time to conduct, but it will be thorough and fair.”

More in News

A wedding and special events’ planning business has agreed to pay a $200,000 settlement to five employees living in the country illegally after allegedly failing to pay them minimum wages and overtime and discriminating against them because of their race.

The CIA has concluded in a secret assessment that Russia intervened in the 2016 election to help Donald Trump win the presidency, rather than just to undermine confidence in the U.S. electoral system, according to officials briefed on the matter.